Making Sodium Hydroxide

[OMG]

I found a link to a thread for this but the link didn't work so I'm not sure what info was in it.

I cant seem to find a box of lye anywhere, but I have a big bag of calcium hydroxide so I thought I would make some using that and sodium bicarbonate.
I figured out the grams needed of each, then heated up and dissolved a bunch of the baking soda, then added the calcium hydroxide slowly and kept it on a steady heat. It bubbled a bit but wasn't actually "boiling".

Is there any way to make the calcium hydroxide more soluble in this reaction (I know its less soluble with an increase in heat but i figured the heat might speed up the reaction enough to offset that).
It has been sitting on the heat for hours now and I'm not sure if its done reacting. When I stir it it still seems like its just lime water, but it does settle and about half of the pot is 'clear' water.
There is about 4 liters of water and the reaction should only produce about 750g of NaOH so all of it should definitely dissolve.

So, how do I know if the reaction is done? Is there a way to know if all the NaHCO3 has reacted?
Would a hint be how fast the solution settles?
Should I expect any problems because I used NaHCO3 instead of Na2CO3?

Na2CO3 + Ca(OH)2 -> CaCO3 + 2NaOH

 

[nicknitro]

OMG,

Your equation looks good. I wonder though is this what you are really looking for?

Base with Base? I am no chemist, but I would think you would want acid + base. Forgive my ignorance, I'm sure it would produce some salts, that would have to be filtered, but. So Ca(OH)2 + NaCl + H2O = CaCl + NaOH +2 H2O. Unsure of heat required to make reaction.


Even if this was true, I doubt it would be of practical value to you. Filter out chlorides, then evaporate to increase saturation?

Can't you just get some crystal drain opener? I've heard of numerous examples here on the forum. I believe one was common Drano crystals.

Sorry if I have mislead you, again I'm not a chemist, just trying to help.

Good Luck,
Nick

 

[peter i]

First, sodium hydroxide is a common household chemical, and should be easily available.

Apart from that, your equations looks good.

When you add sodium carbonate (soda) to calcium hydroxide, the carbonate and calcium ions will react to form insoluble calcium carbonate, just as you wrote.
(In the old days, potassium hydroxide was made from wood ash and calcium hydroxide in just this way)

The calcium hydroxide is however likely to have allready reacted with som CO2 from the air, meaning that you can never expect to dissolve it completely. It is also likely that some CO2 is dissolved in the water you use.


I honestly don't know about the baking soda, but
Na2CO3(aq) + Ca(OH)2(aq) -> CaCO3(s) + 2NaOH(aq)

would be expected to be
NaHCO3(aq) + Ca(OH)2(aq) -> CaCO3(s) + H2O + NaOH(aq)

At least in my area, baking soda is quite a bit more expensive than plain soda.

 

[dick b]

OMG:

Its available on ebay. Check out this link 330314334078 in the search box. They are in Washington State, so they may be able to ship to BC.
I would think that it is available to you at a hardware store or building materials dealer.
Its commonly used to make soap, as a drain cleaner or caustic soda. Lye is not normally used as its name.
Good luck in your search!

 

[LittleJohnnyH2SO4]

Base with Base? I am no chemist, but I would think you would want acid + base. Forgive my ignorance, I'm sure it would produce some salts, that would have to be filtered, but. So Ca(OH)2 + NaCl + H2O = CaCl + NaOH +2 H2O. Unsure of heat required to make reaction.

That second reaction won't occur. It works backwards because Ca(OH)2 is poorly soluble and it's precipitation drives the reaction to the left.

Base and acid are all relative terms. If you're working with grignard reagents (fancy organic chemistry), water is an immensely powerful acid that will ruin the reaction. When you dissolve a strong acid (like sulfuric, hydrochloric, or nitric), water behaves as a base. It accepts a proton from the acid and forms a hydronium ion. This is analogous to ammonia reaction with an acid and forming an ammonium ion. So, relative to water, NaOH is a very strong base, and NaHCO3 is a weak base. relative to each other, NaHCO3 is an acid and the NaOH is the base. (bicarbonate is in the same vein as bisulfate in being a half-neutralized diprotic acid).

I suggest you use carbonate instead because you will get twice the NaOH for the same amount of Ca(OH)2. If purity is an issue, use food grade baking soda instead of the slightly cheaper washing soda and roast it in an oven for several hours in a thin layer until it is a free-flowing powder. Heating a small sample (say in a test tube over a strong flame) should not reduce the weight any more, indicating complete conversion to sodium carbonate

2NaHCO3 + heat -> Na2CO3 + H2O + CO2

Boil any water you use before doing this procedure and minimize air exposure. Store the solution in an airtight plastic container (NaOH slowly dissolves glass and can't be used with PET bottles, as well as some other kinds of plastic. Polyethylene or Polypropylene is your best bet).
To test for the end of the reaction, add a dropperful of HCl, vinegar, or any acid really to a sample of the liquid. If it went as planned, no gas should form at all since all the carbonate is locked up in the CaCO3 precipitate.

 

[OMG]

Excellent, thanks Johnny that was an excellent solution and advise.
I will check for it more closely in hardware stores and look for appropriate drain cleaners.

 

[nicknitro]

Thanks Johnny,

Nice explaination.

Nick

 

[bmgold]

If yoú know of anyone local that makes biodiesel check with them to find out where they get their sodium hydroxide. I once helped a company make biodiesel and we used a case of the stuff each batch. The local hardware store ordered it in for us but I think they had single cans on the shelf too.
Also, there is a way to make lye using salt water and electricity in a divided cell with carbon or graphite electrodes. I don't know the chemistry of the reaction or how much time or current it takes to do it. Maybe someone on the forum could explain how to do it.

 

[Scott2357]

You can make it but why bother when it's cheap and easy to get. I have a local supplier where I can get 50 lb for $65. He has a lot of other good stuff and most all acids too. I can find the website link if anyone's interested.

 

[LittleJohnnyH2SO4]

If yoú know of anyone local that makes biodiesel check with them to find out where they get their sodium hydroxide. I once helped a company make biodiesel and we used a case of the stuff each batch. The local hardware store ordered it in for us but I think they had single cans on the shelf too.
Also, there is a way to make lye using salt water and electricity in a divided cell with carbon or graphite electrodes. I don't know the chemistry of the reaction or how much time or current it takes to do it. Maybe someone on the forum could explain how to do it.

The sideproduct of this reaction is chlorine gas, which is not something you really want a lot of if not necessary. Using an undivided cell generates bleach and chlorates/perchlorates as you continue to run current through it. Graphite electrodes erode and make a huge mess. Plus, it's a pretty slow process.

I'm with the above poster in the call to just buy the stuff. I have several pounds of clean lye prills and make cold-process soap with it fairly regularly. If you don't need a case of the stuff, try soapmaking supply for up to a few pounds. Try the hardware store drain cleaners perhaps. Read MSDS since some brands have all sorts of other crud added.

 

[EVO-AU]

As usual I am dated, but have any of you gentlemen tried 'Thrift' drain cleaner ? 99% sodium hydroxide. About 18 months back purchased 5 #'s for 44$, but when you figure about two tblsp makes a gal. What the heck. Good price and darn good solution. Phill Yeah, they have a website.

 

[Richard36]

There is a way to make lye using salt water and electricity in a divided cell with carbon or graphite electrodes. I don't know the chemistry of the reaction or how much time or current it takes to do it. Maybe someone on the forum could explain how to do it.

The sideproduct of this reaction is chlorine gas, which is not something you really want a lot of if not necessary. Using an undivided cell generates bleach and chlorates/perchlorates as you continue to run current through it. Graphite electrodes erode and make a huge mess. Plus, it's a pretty slow process

I do not know about the possibility of the electrolytic method producing bleach, chlorates, and perchlorates, but the Encyclopedia that I looked it up in did say that all commercial sodium hydroxide is produced by passing electricity through salt water.

12v dc and stainless steel electrodes should work.

I once played mad scientist and passed 120AC through a small container of salt water just to see what would happen, and the reaction was fast! The water turned yellow with the dissolved salt converting to a somewhat clumpy yellow precipitate in about 3 minutes. Slightly thereafter, the electrodes started to arc within the solution, and began to dissolve the electrodes, at which point I turned off the current.

I just thought that I would post my experience, maybe make a few people chuckle.

Sincerely; Rick.

 

[markqf1]

In the electrolytic salt water cell, it's the ph that determines what you end up with.
If my memory serves me correctly, for chlorate a ph of six and a half and, for hypochlorite a ph of ten is what you need. To the best of my understanding, lye is produced as a by-product of this process.

Rooto, in the drain opener section of the hardware store, is 100% lye.

Mark

 

[Irons]

The Sodium Carbonate/ Calcium hydroxide method works quite well. You can buy Calcium Hydroxide as Slaked Lime. Ground limestone lime will not work. Sodium Carbonate is Washing Soda, about .75 cents per pound at the supermarket. It's even cheaper at a chemical supply house.

The reaction is exothermic and is complete in a few seconds. All you have to do is let the Calcium Carbonate settle out and then pour of the Sodium Hydroxide solution. It actually makes a better product than what you can buy because, if you add a small excess of Calcium Hydroxide, it makes a solution almost free of Sodium Carbonate.
The Lye you buy in the store contains a fair amount of Sodium Carbonate and is not as reactive.

Save the Calcium Carbonate for neutralizing waste acid.

I make a slurry of the calcium Hydroxide and pour it into a saturated solution of Sodium Carbonate.

It's actually quite a bit less expensive than the NaOH you can buy. I use poly milk jugs as a reaction/storage vessel.

 

[Richard36]

I just go to hardware stores and read the back of drain cleaner containers untill find one that is pure sodium Hydroxide. It saves time and effort for me.

Sincerely; Rick; a.k.a "The Rock Man".

 

[Irons]

I just go to hardware stores and read the back of drain cleaner containers untill find one that is pure sodium Hydroxide. It saves time and effort for me.

Sincerely; Rick; a.k.a "The Rock Man".

I understand your point but even store-bought NaOH leaves something to be desired. Nothing like opening a new bottle and finding the prills coated with Sodium Carbonate from improper or long storage.
It's easy to fix with a little Calcium Hydroxide added to the make-up solution.
You might find this useful. I was attempting to digest Silica with hot Sodium Hydroxide. Sodium Carbonate is way too slow, but the freshly made Sodium Hydroxide was very aggressive. The solution could be regenerated by pouring it off and adding Calcium Hydroxide. Carbonates and Silicates precipitate out. let it settle, then back to the pot.

 

[Richard36]

I just go to hardware stores and read the back of drain cleaner containers untill find one that is pure sodium Hydroxide. It saves time and effort for me.

Sincerely; Rick; a.k.a "The Rock Man".

I understand your point but even store-bought NaOH leaves something to be desired. Nothing like opening a new bottle and finding the prills coated with Sodium Carbonate from improper or long storage.
It's easy to fix with a little Calcium Hydroxide added to the make-up solution.
You might find this useful. I was attempting to digest Silica with hot Sodium Hydroxide. Sodium Carbonate is way too slow, but the freshly made Sodium Hydroxide was very aggressive. The solution could be regenerated by pouring it off and adding Calcium Hydroxide. Carbonates and Silicates precipitate out. let it settle, then back to the pot.

Fair enough.

I'm "The Rock Man", not "The Chemist", lol!

Good to have you here, and share your chemistry knowledge with us Irons.

Sincerely; Rick. "The Rock Man".

 

[qst42know]

The Sodium Carbonate/ Calcium hydroxide method works quite well. You can buy Calcium Hydroxide as Slaked Lime. Ground limestone lime will not work. Sodium Carbonate is Washing Soda, about .75 cents per pound at the supermarket. It's even cheaper at a chemical supply house.

The reaction is exothermic and is complete in a few seconds. All you have to do is let the Calcium Carbonate settle out and then pour of the Sodium Hydroxide solution. It actually makes a better product than what you can buy because, if you add a small excess of Calcium Hydroxide, it makes a solution almost free of Sodium Carbonate.
The Lye you buy in the store contains a fair amount of Sodium Carbonate and is not as reactive.

Save the Calcium Carbonate for neutralizing waste acid.

I make a slurry of the calcium Hydroxide and pour it into a saturated solution of Sodium Carbonate.

It's actually quite a bit less expensive than the NaOH you can buy. I use poly milk jugs as a reaction/storage vessel.

This is a handy thing to know Irons. I'll try it the next time I need some drain cleaner. Store bought doesn't work very well when it lumps together in the trap.

 

[PreciousMexpert]

Maybe someone can straighten this out for me

I thought about making my own lye
It will cost much more to make than by ready lye
Irons was saying the quality is better when making your own
If someone has a link to a good suppier maybe they can give me the link


http://www.sciencelab.com/page/S/CTGY/21761
calcium hydroxide
125 g $35.49



http://cgi.ebay.com/8-lbs-Sodium-Hydroxide-Lye-Beads-Red-Devil-Lye-Plus_W0QQitemZ110424033704QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item19b5c909a8
8 lbs Sodium Hydroxide Lye Beads Red Devil Lye Plus !

 

[Irons]

Maybe someone can straighten this out for me

I thought about making my own lye
It will cost much more to make than by ready lye
Irons was saying the quality is better when making your own
If someone has a link to a good suppier maybe they can give me the link


http://www.sciencelab.com/page/S/CTGY/21761
calcium hydroxide
125 g $35.49



http://cgi.ebay.com/8-lbs-Sodium-Hydroxide-Lye-Beads-Red-Devil-Lye-Plus_W0QQitemZ110424033704QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item19b5c909a8
8 lbs Sodium Hydroxide Lye Beads Red Devil Lye Plus !

Go to your local Masonry supply and ask them for a bag of Slaked Lime. Around here it's less than $8 US for a 50 pound bag.

You can make Sodium Hydroxide for less than a dollar a pound.